Messages in this thread | | | Date | Mon, 13 Jan 2020 13:22:14 +0000 | From | Morten Rasmussen <> | Subject | Re: [PATCH] cpu-topology: warn if NUMA configurations conflicts with lower layer |
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On Sun, Jan 12, 2020 at 01:22:02PM +0000, Valentin Schneider wrote: > On 09/01/2020 10:52, Morten Rasmussen wrote: > >> AFAIA what matters here is memory controllers, less so LLCs. Cores within > >> a single die could have private LLCs and separate memory controllers, or > >> shared LLC and separate memory controllers. > > > > Don't confuse cache boundaries, packages and nodes :-) > > > > core_siblings are cpus in the same package and doesn't say anything > > about cache boundaries. It is not given that there is sched_domain that > > matches the core_sibling span. > > > > The MC sched_domain is supposed to match the LLC span which might > > different for core_siblings. So the about example should be valid for a > > NUMA-in-package system with one package containing two nodes. > > > > Right, the point I was trying to make is that node boundaries can be pretty > much anything, so nodes can span over LLCs, or LLCs can span over nodes, > which is why we need checks such as the one in arch_topology() that lets us > build up a usable domain hierarchy (which cares about LLCs, at least at some > level).
Indeed. The topology masks can't always be used as is to define the sched_domain hierarchy.
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